Any alternative ideas to fullscreen popup-messages?

[David Ford]

A tiny (mailbox | battery | etc) icon with something to indicate what
type of message was received (sms, imap, etc) that floated down the area
where the scrollbar is commonly located then floated at the bottom right
corner for a moment would be great.  Users could then click on the icon
in the corner or press the context sensitive button to enlarge the icon
to see a quick snapshot or go direct to the mailbox the msg was received in.

That saves a lot of screen space and still gives you several seconds
worth notification plus the means to respond to it.  It keeps the
notification from obscuring nearly all of the viewport and is
sufficiently animated to draw your attention to it, but tiny enough not
to frustrate you by overlaying a large area of the screen and changing
the input focus of what you're doing.

-david